Melophorus isaiah Heterick, Castalanelli & Shattuck

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 234-237

Melophorus isaiah Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from c. 9 km E of Finke, Northern Territory, 30 September 1972, J.E. Feehan, ANIC Ants Vial 15.156 [ANIC32-900184] (ANIC). Paratypes: major worker on same pin and with same details as holotype (ANIC); major worker and two minor workers from Bopeechee Siding, South Aus tralia, 24 July 1956, RSM [sic], QHD3 A97, ' Melophorus fieldi Forel Det. J. J. McAreavey 22 November 1957' [although apparently belonging to the same complex, the two taxa differ in a number of subtle characters, including the head shape, mesosoma and pilosity-BEH] (BMNH); major worker and two minor workers from Bopeechee Siding, South Australia, 24 July 1956, RSM [sic], QHD3 A97 [ANIC32-900058] (MCZ); minor worker from Lake Eyre South, South Australia, 23 September 1980, H. Heatwole P.J. M. Greenslade, (12) (SAM).

Other material examined.

Western Australia: St. Ives GM via Kambalda (Curtin Students [JDM32-001803]).

Diagnosis.

Melophorus isaiah can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the M. fieldi species-complex because of the appearance of the anteriorly placed clypeal psammophore, the compact propodeum, the presence of more than one preapical spine on the metatibia, at least in the major worker, the long, even spindly legs, and the unmodified mandible in the major worker. In full-face view, the eye of all workers is placed very high on the head, and slightly above an imaginary horizontal line separating the head (excluding the mandibles) into equal upper and lower sectors. The high placement of the eyes, especially in the minor worker where they occur at the junction of the vertex and the genae, sets this species apart from all other Melophorus within the M. fieldi species-complex.

Minor worker description.

Head. Head square; posterior margin of head planar or weakly convex; frons shining with superficial shagreenation or microreticulation only; frons consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). Eye moderate (eye length 0.20-0.49 length of side of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae concave; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and mainly smooth, vestigial shagreenation most noticeable on humeri and mesopleuron; anterior mesosoma in profile convex anteriad, mesonotum often slightly overlapping pronotum, mesosoma planar or slightly sinuate posteriad; erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle; propodeum shining and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated at least twice its width from the declivitous face of propodeum, and shorter (length <0.50 × height of propodeum), or situated on or beside declivitous face of propodeum, and shorter (length <0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded; node shining and faintly striolate and microreticulate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae, or consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of sclerite. General characters. Colour brown (gaster usually darker) with legs that are pale yellowish and depigmented distally.

Major worker description.

Head. Head square; posterior margin of head planar or weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only, or consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae straight, divergent posteriad; frontal lobes straight in front of antennal insertion. Anterior clypeal margin broadly convex with anteromedial dimple; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and 4; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining with very superficial microreticulation, entire lower mesopleuron distinctly shagreenate; anterior mesosoma in profile convex anteriad, mesonotum overlapping pronotum, planar or slightly sinuate posteriad; erect pronotal setae short and unmodified, or weakly expanded distally, or erect pronotal setae absent; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; erect propodeal setae present and sparse to moderate (1-12), or variable in number, may be absent; appressed propodeal setae short, separated by more than own length and inconspicuous; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node tapered with blunt vertex; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining with superficial microreticulation, or shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. General characters. Colour of head orange tan or light brown, mesosoma brown, gaster dark brown, legs pale yellowish.

Measurements.

Worker (n = 4): CI 102-118; EI 19-31; EL 0.19-0.28; HL 0.60-1.26; HW 0.62-1.48; ML 0.86-1.50; MTL 0.61-1.05; PpH 0.08-0.15; PpL 0.36-0.63; SI 75-125; SL 0.77-1.11.

Comments.

The facetious scientific name proposed here reflects the relatively high placement of the eyes on the head capsule, which, together with its long palps, are suf ficient to identify the ant. Specimens have been collected in remote locations in the NT, SA and WA, and this may account for the infrequency with which it appears in collections. No specimens were available for sequencing and nothing is known of its preferred habitat or its habits.

Etymology.

A pun on the high placement of the eyes on the head capsule; noun in the nominative singular used without declension.